in src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java [1723:1737]
private void writeConfig(MessageBuilder mb) {
mb.a(" <configuration>").newline();
if (release != null) {
mb.a(" <release>").a(release).a("</release>").newline();
} else if (JavaVersion.JAVA_VERSION.isAtLeast("9")) {
String rls = target.replaceAll(".\\.", "");
// when using Java9+, motivate to use release instead of source/target
mb.a(" <release>").a(rls).a("</release>").newline();
} else {
mb.a(" <source>").a(source).a("</source>").newline();
mb.a(" <target>").a(target).a("</target>").newline();
}
mb.a(" </configuration>").newline();
}